With a known motor according to German Pat. No. 949,697, a roller or anti-friction bearing is provided at each of the two ends of the crankshaft. Only one of these anti-friction bearings can be fastened by means of a press fit or force fit because of technical difficulties; the other anti-friction bearing must be secured with other known means. The arrangement of the anti-friction bearings can only occur after installation of the crankshaft is complete, which makes the installation thereof more difficult and leads to a longer assembly time; for this reason, the assembly of the motor is very expensive. The known arrangement of the anti-friction bearings additionally requires a relatively long overall length, which is undesirable particularly with single-cylinder motors constructed as small or fractional horsepower motors.